Wavelength to Frequency Calculator
Convert wavelength to frequency using c = lambda x f. Quick reference for visible light, radio waves, microwaves and physics class problems.
Last updated: May 2026
Wavelength, frequency and the speed of light
The relationship is straightforward: frequency = speed of light ÷ wavelength. The speed of light in a vacuum is constant at 299,792,458 m/s. Because wavelength is typically measured in nanometres (nm) for visible light, the result lands in terahertz (THz). Green light at 550 nm works out to approximately 545 THz.
Visible light spans roughly 380 nm (violet, ~790 THz) to 700 nm (red, ~428 THz). Below 380 nm lies ultraviolet; above 700 nm is near infrared. X-rays fall in the 0.01 to 10 nm range.
Electromagnetic spectrum: wavelength and frequency reference
| Band | Wavelength range | Frequency range | Common use |
|---|---|---|---|
| Gamma rays | Below 0.01 nm | Above 30,000 THz | Cancer radiotherapy |
| X-rays | 0.01 to 10 nm | 30 to 30,000 THz | Medical imaging |
| Ultraviolet | 10 to 380 nm | 790 to 30,000 THz | UV sterilization |
| Visible - violet | 380 to 450 nm | 670 to 790 THz | Human vision |
| Visible - green | 495 to 570 nm | 526 to 605 THz | Peak eye sensitivity |
| Visible - red | 620 to 700 nm | 428 to 484 THz | Traffic lights, lasers |
| Near infrared | 700 to 2,500 nm | 120 to 428 THz | Remote controls, cameras |
| Mid infrared | 2,500 to 25,000 nm | 12 to 120 THz | Thermal imaging |
Frequently Asked Questions
What wavelength is visible light?
380 nm (violet) to 700 nm (red), corresponding to roughly 430-790 THz. The default 550 nm is the centre of the green band, close to the peak sensitivity of the human eye under daylight conditions.
Why is frequency calculated from wavelength rather than measured directly?
The speed of light in vacuum is a physical constant (299,792,458 m/s). Because frequency × wavelength = c, knowing one gives the other exactly. Wavelength is easier to measure in optics (using diffraction gratings); frequency is easier in radio electronics (using oscillators). This calculator handles the conversion either way.
What electromagnetic spectrum ranges does nanometre wavelength cover?
Visible: 380-700 nm. Near UV: 10-380 nm. Near IR: 700-2500 nm. Mid IR: 2500-25,000 nm. X-rays: 0.01-10 nm. Gamma rays: below 0.01 nm. Radio waves start in the millimetre range (1,000,000 nm and above).